Fluid won't go through a hollow-moving-effector, they just move aside

Question

Obligatory kinda new to blender, have just been following some little tutorials here and there.

Background about my project : I'm trying to make an archimedes screw. Basically it is made of a long metal rod as an axis and curving around it is a helix pipe. It rests on a 30° ish angle from the river/water, so that when the whole thing rotate around the rod axis, the tip will dip intonthe water each rotation and water will go up by some magical physic power.

What i did : Following some tutorials about fluid, i managed to make a flowing river with cube as the inflow shape and bigger cube as the domain. I also managed to make the rotating helix with a circle shape and screw modifier, then i deleted both the cap faces, and added solidify. I have also doubled my resolution to 64 (edit : 120) since i thought that might be the problem.

The problem : But even when i chose my hollow moving helix as the effector, and after i checked that the helix color was blue in the face orientation, the water just didnt want to go into the pipe, they just went around it for each rotation as a simple obstacle.

Any ideas about this? Thanks in advance.

Edit : Blend file https://pasteall.org/blend/22c63053a57b403aacf56fad30186c75

Screenshot :

(this one is collision setting of the helix)

(this one is for domain of my box)

Answer 1

I've downloaded your file and changed a few things to make it work: first of all I disabled Only Rim in the Solidify Modifier of the screw. That way your pipe has an inner wall with face normals pointing in the right direction.

Then the Domain Resolution of 120 is too small for your pipe. It measures around 30 cm on the outside while a voxel at that resolution is about 5.5 cm big. In combination with possible margin issues there's not much open space for the voxels to enter the pipe. I've set the resolution and now (some) liquid goes into the pipe.

And I've expanded the length of the animation to 250 frames, even then the fluid hasn't gone very far up the pipe. If you want it to climb further up, the animation needs to be quite a bit longer.

Finally I've set the Particle Radius of the Mesh to 1.2 instead of 2, so that the fluid doesn't look more like a blob, although with the higher Domain Resolution this might not have been necessary.

Answer 2

I am pretty sure the reason are the normals.

If you have an effector in a fluid the outside (which is shown as blue if you turn on face orientation)

will "react" to the fluid so the fluid cannot go inside an object.

if you flip the normals, the fluid (which is inside) cannot get out.

In your case - you want both. So i would suggest you make two screws - one outside with "normal" normals and one a bit littler and flipped normals so that the water keeps inside. This could work.